Glassware is conventionally formed in so-called individual section or IS machines in a process in which a molten glass gob is first preformed in a parison mold, from which it is transferred to a second mold in which it is blown to final shape. In the parison mold, the gob is either blown to parison mold shape forming the so-called blow-and-blow process, or pressed by a plunger into the parison shape forming the so-called press-and-blow process. U.S. Pat. Nos. 2,289,046 and 3,024,571 show IS machines for press-and-blow manufacture of glassware.
As part of the gob weight control system in press-and-blow IS machine glassware manufacture, a sensor is employed to measure plunger travel at the end of the plunging stroke to infer the amount of glass in the parison mold. See, for example, U.S. Pat. Nos. 3,192,027 and 4,369,053. A sensor core of ferromagnetic construction is mounted on the movable plunger piston rod, and cooperates with a fixed sensor coil to supply a signal indicative of final plunger position through a cable to a distribution box, from which the signals from all of the sensors in the various sections of the IS machine are fed to a control computer. For maintenance or trouble-shooting of the sensor and cable, a technician must employ general purpose test equipment, which is suitable primarily only for locating open- or short-circuit conditions, and not for quantitatively measuring electrical characteristics of the sensor or cable, or for measuring operating characteristics such as sensor output as a function of plunger position.
It is therefore a general object of the present invention to provide an apparatus and method for testing the cable and sensor arrangement. A more specific object of the present invention is to provide an apparatus and method of the described character that are inexpensive to manufacture and easy to use, and that are adapted not only to test for open-circuit and short-circuit conditions at the sensor or sensor/cable system, but also to test operating characteristics of the sensor such as sensor output at full stroke of the mold plunger. Another object of the present invention is to provide a test apparatus of the described character that may be readily calibrated by the operator.
A test apparatus for measuring operating characteristics of a position sensor coupled to a parison mold plunger for glass gob weight control in a press-and-blow individual section glassware manufacturing machine in accordance with the present invention includes circuitry for connection to the sensor to provide a signal as a function of electrical characteristics thereof, a switch network for selecting among a plurality of differing electrical characteristics to be measured, and a display responsive to the sensor signal for displaying the selected and measured electrical characteristic of the sensor to an operator. The measurement circuitry includes a measurement bridge for measuring resistance characteristics of the sensor, and an amplifier circuit for measuring sensor output as a function of position of the plunger. The switch network selectively connects the sensor signal to the measurement bridge and amplifier circuit in differing modes of operation of the test apparatus.